Reducing Imidacloprid Clipping Residues Via Formulation Selection and Irrigation.

Imidacloprid is a systemic insecticide used for controlling various soil-borne pests in turfgrass sites including athletic fields, golf courses and residential properties.  Imidacloprid plant uptake occurs via foliar and root pathways, and is acropetally translocated, making it more likely to accumulate in the upper region of treated turfgrass plants that may be removed during a mowing event, clippings.  Field research was initiated August 13, 2015 in Raleigh, NC to quantify imidacloprid residue in clippings from hybrid bermudagrass [Cynodon dactylon (L.) Pers. × Cynodon transvaalensis Burtt-Davy, cv. ‘Tifway 419’] maintained at 5 cm.  Experiments quantified residues in clippings from areas treated with imidacloprid (0.44 kg ai ha^-1) via two formulations (granular or liquid) and following two post-application irrigation timings (0 or 4 h after treatment [HAT] following liquid application only).  Clippings were collected from plots treated 32, 16, 8, 4, 2, 1 or 0 d before clipping collection (DBCC).  Results suggest formulation and post-application irrigation timing affect imidacloprid residue in clippings.  Granular application resulted in 39.9% less of the applied imidacloprid compared to liquid application (47.1% of applied) in clippings collected from areas treated 0 DBCC, while irrigating 0 HAT resulted in 40.8% less of the applied compared to 4 HAT (48.3%).  Additionally, granular application and immediately irrigating liquid application resulted in nondetectable imidacloprid residues in clippings collected from 8 to 32 DBCC, while residues remained detectable through 32 DBCC following liquid application, irrigated 4 HAT.  Information from this research will assist practitioners’ ability to reduce off-target imidacloprid transport potential via improved application practices.